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1/22/2018 12:00 pm1/22/2018 America/ChicagoICMT Seminar: "The effects of disorder in the bulk and on the boundary of Weyl semimetals""
DESCRIPTION:

We will discuss the effects of short-range disorder on three-dimensional Weyl semimetals. We first focus on the proposed quantum critical point (QCP) separating a semimetal and diffusive metal phase driven by disorder. We establish the existence of two distinct types of excitations in the weak disorder regime. The first are perturbatively renormalized dispersive Weyl states and the second are quasi-localized “rare” eigenstates. We find that these rare eigenstates contribute an exponentially small but non-zero density of states at zero energy, which destabilizes the semimetal phase and converts the semimetal-to-diffusive metal transition into a cross over (dubbed an avoided quantum critical point). In turn, it is no longer obvious how robust the topological properties are in these materials. We will therefore also discuss the effects disorder has on the robustness of Weyl Fermi arc surface states. We find that the Fermi arcs, in addition to having a finite lifetime from disorder broadening, hybridize with the nonperturbative bulk rare states which unbinds them from the surface (i.e. they lose their purely surface spectral character). Thus, we provide strong numerical evidence that the Weyl Fermi arcs are not topologically protected from disorder. Nonetheless, the surface chiral velocity is robust and survives in the presence of strong disorder, persisting all the way to the Anderson insulating regime by forming local current loops into the bulk that live within the localization length of the wavefunction.

\n\nSPEAKER:

Jed Pixley, Rutgers

190 ESB

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ICMT Seminar: "The effects of disorder in the bulk and on the boundary of Weyl semimetals""

We will discuss the effects of short-range disorder on three-dimensional Weyl semimetals. We first focus on the proposed quantum critical point (QCP) separating a semimetal and diffusive metal phase driven by disorder. We establish the existence of two distinct types of excitations in the weak disorder regime. The first are perturbatively renormalized dispersive Weyl states and the second are quasi-localized “rare” eigenstates. We find that these rare eigenstates contribute an exponentially small but non-zero density of states at zero energy, which destabilizes the semimetal phase and converts the semimetal-to-diffusive metal transition into a cross over (dubbed an avoided quantum critical point). In turn, it is no longer obvious how robust the topological properties are in these materials. We will therefore also discuss the effects disorder has on the robustness of Weyl Fermi arc surface states. We find that the Fermi arcs, in addition to having a finite lifetime from disorder broadening, hybridize with the nonperturbative bulk rare states which unbinds them from the surface (i.e. they lose their purely surface spectral character). Thus, we provide strong numerical evidence that the Weyl Fermi arcs are not topologically protected from disorder. Nonetheless, the surface chiral velocity is robust and survives in the presence of strong disorder, persisting all the way to the Anderson insulating regime by forming local current loops into the bulk that live within the localization length of the wavefunction.

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